A GAF zoom lens I obtained recently in a projector needed cleaning, so I took it apart and cleaned the elements. I was determined to do it carefully so I could put it back together correctly. Well, the individual pieces love to flip-over before you know what's going on, so now there are at least 2 elements that might not be oriented correctly. I've been doing trial an error, but the projected image will not focus correctly. (It focused fine before my "efforts".) The image is much brighter now since one of the inner elements was fogged up before. The best I can get is partial focus on some areas of the image, but then other areas go out of focus. Pretty much either the inner areas or outer areas will foucs, but not all at once.

I can't find one schematic, so to speak, of a typical 8mm projector lens anywhere on the internet, though there are plenty of people describing how they took apart lensed and cleaned them. There are some sites that talk about zoom lens principles, with diagrams, but it hasn't helped.

There are definitely 4 permutations of orienting the individual lens elements. There may be 8, but one element looks like it can be oriented either way. This one likes to flip when you remove it, so I can't even be sure if I'm reorienting it. I'm 99.99% sure that there is no difference from one side to the other. (It's convex.)

I swear I've tried the first 4 permuations, some are really bad, but none are correct. The 2 elements for those permutations I was careful with by marking one side of them with tape. I'm stumped as to why I can't get this re-assembled correctly.

One element I didn't even remove (didn't have to, since I could clean both sides in place), else I would have potentially 16 permutations!

The outermost element, closest to the screen, is quick to re-orient. For the others, I need to remove 3 screws, and use a lens spanner wrench.
That outermost element is convex-concave. I was sure I marked it correctly, with the concave side facing outward toward the screen, but having the convex side facing the screen seems to make more sense.

Any ideas?

Again, it's not the projector since it focused fine before I took the lens apart.

Not my pic, but my lens is exactly the same.


Thanks